W208 Hazards Flashing Random

[steveoelliott]

Hi,

I've noticed on a couple of occasions now that after locking my CLK, after a few minutes the hazard lights are flashing very fast. Is this a sign of something? Or is something wrong?

Thanks...

 

[steveoelliott]

I have just tested my alarm siren and it works so not related to a bad siren like some other posts I found on here.

 

[flango]

Mine do it if door or boot is not closed properly, door or boot switch

 

[steveoelliott]

If I do this then the siren goes too. All doors / boot shut.

 

[Dec]

The siren contains the brain of the alarm, the alarm PCB, located inside the siren could be damaged, the alarm can still behave normally when tested but still give false triggers.

If an alarm is triggered it will sound the siren for 30 seconds and continue to flash the hazards… at double there normal flashing speed… for a further two and a halve minutes… 3 minutes in total. After this period the alarm should reset itself.

If the alarm is being triggered, which fast flashing hazards indicates, then the siren should also be sounding.
Double (fast) flashing of hazards indicates that the alarm is triggered and is accompanied by 30 seconds of sound from the siren, if the siren is not sounding then its not likely to be a legitimate trigger and more likely to be a faulty siren.

For the alarm to be triggered, a door/boot/bonnet switch would need to be activated either manually or because it is defective in some way OR there is an ailing car battery, a sudden drop in voltage is also an alarm trigger.

Dec

 

[Dieselman]

Possibly the alarm battery.

 

[WG M-B]

As above check all is shutting down as it should (ie the interior lights are switching off) . This will confirm the switches on the doors are making contact.
If this is ok it could be any of the sensors associated with the ATA system. Most probably the siren but it can be others

 

[steveoelliott]

Thanks for the feedback guys...

So either way it looks like yet another electrical fault that has to be diagnosed.

If this persists will get the local indy to look at it.

 

[steveoelliott]

Is it worth me disconnecting the siren? Will this act as a workaround?

Will this stop the hazards flashing as they do?

Would just taking out fuse 5 from the trunk do the same trick, this is the alarm siren?

 

[Dec]

You could try the fuse, if not disconnecting siren it will stop all flashing, including when you lock/unlock, be aware you will be voiding your car insurance as you are insured on the basis that you have a working alarm system in the car.

What’s triggering the alarm is contained within the siren, disconnection the siren will stop the false alarms, try the fuse first, I’ve never fiddled with it so not sure what will happen when it is removed… the alarm siren might sound off when you remove it, let us know how you get on,

You can replace the siren for about £80 if you DIY.
Unbolt the siren from the car before you unplug it as it should sound off as soon as it is disconnected at its plug.

Dec

 

[steveoelliott]

Thanks Dec.

Well, I took the fuse out earlier briefly. Nothing happened.

When I set the alarm off by opening the door with the key, just the hazards flashed with no siren.

So taking out fuse is basically doing the same as disconnecting? I just want to be sure it's this before wasting £80. The siren does work so I thought it would be strange to be this.

 

[Dec]

I would expect the alarm not to work at all with the fuse removed but don’t know for sure what happens to the alarm with the fuse removed.
The only sure way is to disconnect the alarm siren, if the siren is at fault then the hazard fault will stop.

Did you try to lock or unlock the car with the remote while the fuse was removed?

The alarm is sound and lights, when its triggered, you set off the alarm but got no sound so that confirms a fault in the siren.

Below link shows what happens to these sirens after about 10 years , I replaced my own last year which was in a similar state of decay.
Alarm / Siren Issues : Goes off for no reason/Kills Battery FIX DIY.. - MBWorld.org Forums

Dec

 

[steveoelliott]

My car still locks / unlicks with the alarm fuse removed.

When I trigger the alarm myself, the siren does not go off when the fuse is removed, just the hazards blink. But with the fuse in place both the siren and hazards flash when triggered.

This is why I am not sure it is the siren but will give it a go.

 

[Dec]

The car should lock/unlock with the fuse removed.
The car should lock/unlock with the siren disconnected.

With the fuse in place, as it should be, the alarm is working normally when tested, the outstanding issue is the false alarms without sound from the siren, there is nothing else to cause the fast flashing other than the alarm siren, I have never heard another explanation for this other than an alarm siren fault.

With regarding to there being a faulty door switch, my alarm system is the same as yours, when I lock the car with the remote, the hazards flash 3 times… if I leave a door or boot open and then lock the car with the remote then the hazards flash 2 times, this is to alert that a door/boot is not shut.

As a matter of interest, what year is the car and to your knowledge has the alarm siren ever been replaced since the car left the factory

Dec

 

[steveoelliott]

Thanks...

I'm going to take the fuse out today and give it a go.

It's a 2000 CLK Conv. Never had siren changed, I knew the previous owner.

 

[Dec]

Which one is your siren?
Dec

 

[steveoelliott]

I haven't got round to taking it off yet. I understand it's by the N/S front behinf fog lamp (UK model).

I took fuse out today, keeping fingers crossed.

 

[Dec]

Not sure what its location is, best to set it off to listen for its location.
Check PM

Dec

 

[steveoelliott]

Seems the fuse removal has done the trick. Need to get a new siren then...